Drilling boreholes with explosive charges



Dec. 25, 1962 L. H. ROBINSON, JR 3, 0, 10

. DRILLING BOREHOLES WITH EXPLOSIVE CHARGES Filed Nov. 27, 1959 4Sheets-Sheet 1 FIG. I.

INVENTOR. LEON H.ROB|NSON JR.,

BY 49 j ATTORNEY.

Dec. 25, 1962 L. H. ROBINSON, JR 3,

DRILLING BOREHOLES WITH EXPLOSIVE CHARGES Filed'Nov. 27, 1959 4Sheets-Sheet 2 FIG. 3

FEG. 6A.

INVENTOR.

I! LEON H. ROBINSON JR..

ATTORNEY.

Dec. 25, 1962 1.. H. ROBINSON, JR 3,070,010

DRILLING BOREHOLES WITH EXPLOSIVE CHARGES Filed Nov. 27, 1959 4Sheets-Sheet 3 FIG. ll.

FIG. 7.

INVENTOR. LEON H. Roams ou JR.,

I ATTORNEY.

Dec. 25, 1962 1.. H. ROBINSON, JR 3,0

DRILLING BOREI-IOLES WITH EXPLOSIVE CHARGES Filed Nov. 27, 1959 4Sheets-Sheet 4 fflffllIf/lI/I fill!!!IIIlllllIlrlllflllIlll/IllllIfI/llllf/lllllll JET CHARGE SEATED"FIG..|2.

E G R A H C E G U A G JET CHARGE OM E T. u G l F GAUGE CHARGE FIRED FIG.i5.

INVENTOR.

LEON H. ROBINSON JR.

ATTORNEY.

3,070,010 DRILLING BOREHULES WITH EXPLGSIVE CHARGES Leon HaynsworthRobinson, In, Houston, Tex., assignor, by mesne assignments, to JerseyProduction Research Company, Tulsa, Okla, a corporation of DelawareFiled Nov. 27, 1959, Ser. No. 855,899 9 Claims. (Cl. 102-2l) Thisinvention relates to the drilling of boreholes, and more particularly todrilling boreholes utilizing a succession of explosive charges includingshaped jet charges.

In connection with drilling boreholes for the purpose of exploitingpossible hydrocarbon deposits in the earth, it has been known to utilizeexplosive charges for the purpose of expediting drilling operations. Ithas also been known to use shaped jet charges in combination withnondirectional blasting charges. Examples of the prior art use ofexplosive charges for drilling operations may be found in U.S. PatentNo. 2,897,756 to L. Borins et al. and U.S. Patent No. 2,587,243 to W.Sweetman.

Previous attempts to use explosive charges for earth drilling have beencharacterized by very slow penetration rates, great expense, and thenecessity for using more or less cumbersome equipment. While thedevelopment of shaped jet charges has made the use of explosives fordrilling more attractive because of the directional characteristics ofthe shaped charge, it has not proved to be a cure-all for thedeficiencies of explosive drilling. A prime reason is that, while theshaped charge is capable of penetrating further into the earth than cana nondirectional explosive charge, it blastsa hole that is quite wide atits mouth but which narrows rapidly and terminates in an elongatedcavity that is far too narrow to accommodate a well or drill pipe. Theuse of blasting charges in the manner taught by the. aforecited Borinset al. patent has not particularly helped the situation because theblasting charges do not deepen or widen the hole drilled by the shapedcharge to any great extent.

The present invention makes use of a well pipe having a landing seat ornipple at or near its lower end. The well pipe is connected toconventional mud circulating equipment at the surface so that drillingfluid is pumped down the well pipe and up the annulus around the wellpipe. Use is made of elongated shaped jet charges and elongatednondirectional gauging charges adapted to be pumped down the Well pipe,and further adapted to seat on the landing nipple or seat so that adifferential pressure is built up thereacross.

The jet charges and gauging charges are injected into the stream ofdrilling fluid going down the well pipe, according to a predeterminedsequence. First, a shaped charge is pumped down the well pipe. After itseats on the landing seat, the explosive portion of the jet charge isspaced from the bottom of the borehole a predetermined distance ofpredetermined magnitude that is built up across the shaped charge.Responsive to differential pressure, the charge is detonated so as toblast a hole in the earth at the bottom of the well bore. A gaugingcharge is ,then landed on the seat so as to extend into the holeproduced by the preceding shaped jet charge. Preferably, the gaugingcharge is long enough to penetrate sub stantially the entire length ofthe hole blasted by the shaped charge. The gauging charge, which may beof a brisant or unbrisant explosive material or a combination thereof,is detonated while tamped with drilling fluid and preferably while undera hydrostatic pressure of at least 1000 psi. Drilling fluid iscirculated after each detonation of a shaped charge and a gauging chargeso as to remove earth fragments and fragments of the explosive chargehousing. Preferably, the explosive charges are injected ment that may beused at the earths surface in connection with the practice of theinvention;

FIG. 2 is a View of a shaped jet charge being pumped down a well pipe,showing a preferred construction of the lower end of the well pipe;

FIG. 3 is an elevational view, partially in section, of the explosivecharge magazine housing shown in FIG. 1,

which view shows certain of the details of the magazine housing;

FIG. 4 is a fragmentary cross-sectional view taken along section 44 ofFIG. '3;

into the-drilling stream so as to be spaced apart substan- FIG. 5 is ain FIG. 4;

FIG. 6 is a cross-sectionalview taken along section 6-6 of FIG. 3; I

FIG. 6A is a fragmentary top charge container shown in FIG. 3;

FIG. 7 is a side view, partiallyin cross-section, of a preferred jetcharge capsule to be used in connection with the invention;

FIG. 8 shows certain details of the firing collar shown in-FIG. 7;

FIG. 9 is a side view of a of FIG. 7;

FIG. 10 is a cross-sectional view showing the differential pressureresponsive firing mechanism shown in FIG. 7;

FIG. 11 is a-side view, partially in cross-section, of a gauging chargeto be used in connection with the present invention; and

FIGS. 12, 13, 14, and 15 illustrate successive steps in the use ofexplosive charges for drilling according to the teachings of the presentinvention.

In FIG. 1 there is shown surface equipment for use in connection withthe present invention. The usual drilling rig 1 is provided with anexplosive charge loaders platform 3 at a distance above the drillingfloor 20 determined by the length of well or drill pipe to be run intothe hole to be drilled with the apparatus. An explosive charge housing 5for storing explosive charges is located on the loaders platform 3.

The usual traveling block 9 is suspended from a crown block (not shown)by cables in the usual manner. Located between the swivel 19 and hook 10is an explosive charge magazine housing 17 which is illustrated indetail in FIGS. 3 through 6 and 6A. Connected to swivel 19 is a Kellyjoint 18 which extends through the rotary table 21 into the surfacecasing 25. The function of the magazine housing is to provide a remotelycontrolled apparatus for injecting a plurality of explosive charges intothe'well according to a predetermined sequence. Drilling fluid iscirculated through the magazine housing 17 into the view of theexplosive portion of the firing collar swivel 19 and Kelly joint 18 fromthe usual standpipe 15 and hose connection 13. A mud pump (not shown)supplies pressurized drilling fluid to the stand-pipe. Below thedrilling floor 20 is located the usual mud return line '27 which may becontrolled by a valve 29. The mud control line is hydraulically coupledto the annular space around the drill pipe in the usual manner.

As shown most perspicuously in FIG. 2, the drill or well pipe .28 isprovided with a landing seat 31 at or near Patented Dec. 25, 19-62 topview of the magazine housing shown i 3 its lower end. The purpose ofthis landing seat is to receive a collar 45 fitted around an explosivecharge'33 which is pumped down the well. When the collar 45 lands on theseat 31, flow of drilling fluid downthrough and out the lower end of thewell pipe will be either stopped or substantially reduced so that adifferential pressure will be built up across the explosive charge' 'Aswill be described in detailbelow, differential pressure used for thepurpose of firing the explosive charge;

The details of the explosive charge magazine housing 17 are shown inFIGS. 3,4, 5, 6, and 6A. The housing 17 is suspended from the travelingblock by' the'us'ual hook 10 and bales 11. A housing bonnet'127 isconnected to the lower part 129 o'f'the magazine housingby a pluralityof bolts 135 connecting together the housing flangeslsl', 132. Adrilling fluid inlet port 122 and an exhaust port 152 are provided inthe housing 17. A coupling pipe 123 interconnects the inlet port to thedrilling fluid hose 13. The exhaust port 152 is connected to swivel 19by suitable pipes and a valve 155. The housing is also provided with anadditional port134A in housing bonnet 127 for the purpose of loadingthemagazine with charges. A' suitable plug 132 is provided for thepurpose of sealing port 134A after the magazine has been loaded withexplosive charges, so that drilling fluid cannot escape from the housingthrough port 134. i V

Enclosed within magazine housing 17 is an explosive charge transportmember 147 comprising an upper end section 134, a lower end section 136,and aplurality of tubes which are designated by Roman numerals I throughXI for the purpose of acting as open-ended explosive charge receptacles.The transport member is supported between shafts 105 and 139 whichrespectively extend through the bonnet127 and the lower portion 129 ofthe magazine housing. Shafts 105 and 139, respectively, include bearingflanges 101 and 140, which respectively are fitted between bearingmembers 108 and 144. The hearing members 108 and 144 are respectivelypositioned in the ends, of the housing bonnet 127 and lower housingmember 129. Retaining nuts 107 and 142 are provided for the purpose ofholding the shafts 105 and 139 in place. A ratchet gear or wheel 101A isaflixed to the upper end of shaft 105. As shown most perspicuously inFIG.

5, a solenoid-actuated pawl 111 is positioned on the housing bonnet 127by guide member 113 to engage the' notches in the ratchet wheel 101. Thenotches are provided with small recesses at the bottomsthereof so as tominimize back-lash when the pawl engages theratchet wheel. The pawl maybe biased by a spring means in the conventional manner to normally. fitinto the notches of the ratchet wheel; The solenoid, 110, is providedfor the purpose of momentarily disengaging the pawl from the notches.control eable 121 which extends to the drillerspbsition on the derrickfloor. A small hole 11013 is provided in the housing bonnet 127 and aneye 110C is provided in the The solenoid may be energized through a"pawl 111 so that the pawl may be locked; out of engage- V ment with thenotches of the ratchet wheel by means of pin 110A. An auxiliary pawl115, which may be springbiased intoengagement with the ratchet wheel andwhich may pivot around a pivot point 119,1 isprovided for the purpose ofengaging the ratchet wheel and .to permit counterclockwise movement oftheratchet wheel when the? shaft is manually turned in acounterclockwise direction. 'Pin 119A is adapted to fit through. eye1198 into,

hole 119B to lock the pawl out of engagement with the ratchet wheel.Pawl 115 is normally spring-biased into engagement with the ratchetwheel by means of a spring (not shown) which tends to rotate it in acoun'terclockwise direction as viewed in FIG.'5. V

Inasmuch as the. explosive charge capsules contemplated for use inconnection with the present inventionare corisiderably less dense thanthe drilling mind that 'isordinarily used, the charges will tendtofloa't ini the drilling mud. For thepurpose of holding the explosivecharges within the receptacles in the transport member, there isprovided at the top or each receptacle a flipper "member '137. Theflipper is normally held in a horizontal position by a spring means (notshown) and is rotated to a vertical direction when an explosive chargeis slid into the recep tacle corresponding thereto. As soon as theexplosive charge is in the receptacle, the flipper 137 will swing to ahorizontal position to prevent the explosive charge from floating up outof the receptacle In each of the receptacles there are a nu mber ofports 150 for the purpose of permitting free fluid flow through theinterior of the housing. Likewise, ports 148 and 138 are provided forthe same purpose in the upper and lower portions of the transportmechanism.

. A spiral spring is afiixed to a bar or strap 14]. and to the lower endof shaft 139. The .spring spirals in a manner such that it will be woundwhen the ratchet wheel 101A is rotated in a counterclockwise directionas viewedin MG. 5.' Thus, the spring will tend to rotate shaft 139responsive to withdrawal of pawl 11.1 froma notch of the ratchet wheelafter thespring is wound. Strap or bar 141 is bolted to the lower end.of the housing 17.

FIGS. 7, 8, 9, and 1 0 illustrate a preferred embodiment for the shapedjet charge, its container, and the firing I collar illustrated in FIG.2. As shown in FIG. 7, the

brisant explosive charge material 43 is encapsulated in vided a firingmechanism 37 for the purpose of firing the detonator 39 responsive to apredetermined differential pressure across the opposed ends of theexplosive charge container. The details of the firing mechanism will bedescribed below with reference to FIG. 10. Inasmuch as the use of ashaped jet charge is contemplated, the usual conical liner 47 isprovided. At the upper and lower ends of the container 33 there areprovided stop members 35 and '49. The purpose of the stop members. is tohold a seating ring or firing collar 45 on the charge container. Thefiring collar is longitudinally slidable'along housing 33 and has atapered lower surface for'the purpose of seating on the seat 31 at thebottom of the drill pipe so that a differential pressure can be producedacross the charge. A frangible sleeve 46 is attached to the upper end ofcollar 45 by a suitable adhesive, the sleeve 46 serving to keep thecollar 45; properly aligned on the housing 33. The details of the firingcollar are best illustrated in FIGS. 8 and 9. The firing collar isformed of members 53 and 55 and locking members 57 and 59. The purposeof the locking members is to prevent the firing collarfrom coining apartbefore the charge is' fired and to permit the firing collar to collapseinwardly when thecontainer is destroyed by firing the charge. As shownin FIG. 9, the outer edges of the locking members have a V shape so'that they will not drop away from the members'53"'and 53 when in lockingengagement therewith.

The details of the firing mechanism areshownin FIG.

10. The firing mechanism includes a housing 63 having 73 extends intothe interior of the housing 53. A flexible,v

resilient diaphragm 61 of rubber-likematerial such as neoprene seals theinlet tube 64. A similar diaphragm 75 seals the outlet tube 73. Theinterior of the housing 63 thus is fluid-tight andis filled with water,glycerin, or other suitable, substantially incompressible liquid. Arelease collar '65. is in sliding fit over the tube 73. A spring 71normally biases the release collar 65 away from the tube 73so that itengages the tube 64 of the'inlet port. A firing pin '67 is pivotedabouta pivot'member 69 and is springbiased by means of. spring 63 torotate'counter} clockwise as shown' in FIG; 10. The firing pin will besample released when release collar 71 is moved to the right so as tostrike detonator 39 at one end of its arc of movement. The releasecollar is moved to the right when a sufiiciently large differentialpressure exists between the inlet tube 64 and the low pressure tube 77.The differential pressure will cause diaphragm 61 to bulge downwardlyinto the housing 63 so as to force the release collar to the right andrelease the firing pin'67 so that it will strike the detonator 39.

The diaphragms 61 and 75 are not absolutely necessary, but serve to keepclean fluid around the working parts of the firing mechanism. This isdesirable to insure that the firing mechanism will function properly.

FIG. 11 illustrates a gauging charge particularly adapted for use withthe present invention. The gauging charge comprises a housing 78 similarto the housing used with the shaped charge. A firing collar 45a isprovided that is similar to firing collar 45. A frangible sleeve 46a isalso attached to the collar 45a. The firing mechanism 37a may besubstantially the same as firing mechanism 37. A low pressure tube 77aextends from the firing mechanism 37a to the lower end of the chargecontainer in the same manner as described above with respect to lowpressure tube 77. A substantial section of the lower portion of thecontainer is filled with a brisant or unbrisant explosive material ora'mixture of brisant and unbrisant explosives. There is no conical linerprovided with the device so that the explosive effects of the gaugingcharge are substantially nondirectional. A stop 85 is provided abovethe'topmost level of the explosive so that firing collar 45a will landon seat 31 in such a manner that the topmost level of the explosivecharge will be spaced from the bottom of the well pipe. The housing 78is also provided with an upper stop 84. This construction is for thepurpose of preventing damage to the well pipe when the explosive chargeis detonated. The container may be formed of a frangible material so asto be destroyed easily. The blasting cap 79, when struck by firing pin67, will be detonated and will ignite a length of primacord 81. Tofacilitate destruction of the container, the primacord may be wound in aspiral around the inner surface of the container. Also, an auxiliarydisintegrating charge 83a of tetryl or like material may be used tocomplete the destruction of the container. The container may be formedof a plastic material. A particularly suitable explosive for use inconnection with the gauging charge is PETN or composition B(RDX andTNT). Other suitable explosives may be found on page 4 of the text TheScience of High Explosives by M. A. Cook (Reinhold Publishing Company,1958). The length of the lower end of the container 78 containing theexplosive preferably is long enough to extend substantially the lengthof the hole blasted by the shaped charge.

The operation of the apparatus described in FIGS. 1 through 11 will beexplained with reference to FIGS. 12, 13, 14, and 15. Before theapparatus described above is used, a borehole may be drilled in theearth through the relatively soft earth formations near the earthssurface by means of conventional rotary drilling equipment.Alternatively, the apparatus described above may be utilized from thetime that the well is spudded. However, it usually will be found to bemore economical to use a rotary drilling procedure for the initialstages of drilling the borehole until relatively hard earth formationsare encountered.

When a hole has been drilled to a desired depth in the conventionalmannr, the rotary drill pipe may be pulled out of the hole and a thinnerwalled pipe 28 such as shown in FIG. 2 and FIGS. 12 through 15 may besubstituted therefor. An advantage associated with utilizing thinnerwalled pipe is that larger explosive charges can be run down the pipe.The lower stand of the pipe may be provided with reamer blades 28a forthe purpose of reaming the hole should such become necessary. Likewise,the lowermost edge of the pipe may be studded with diamonds torotary-drill for short time intervals should relatively soft earthformations be encountered.

Plug 132 (see FIG. 5) is removed from the magazine housing, pawl 111 islocked out of engagement with ratchet wheel 101, and pawl 115 is allowedto engage the ratchet wheel. Explosive charges are inserted into themagazine housing into each of the explosive charge receptacles. Thecharge transport means is rotated by a wrench or other means thatengages the hex end 103 of shaft 105. When the transport mechanism isfully loaded with explosive charges, with shaped charges, and gaugingcharges in a predetermined sequence around the mechanism, pawl 111 isreleased to engage the ratchet wheel and pawl 115 is locked out ofengagement with pin 11%. Seal 132 is locked into position and drillingfluid pressure is applied so that drilling fluid is circulated down thewell pipen Initially, a shaped charge 33 is injected into the drillingfluid stream. At intervals of approximately 1 to 10 minutes, the drillermay inject the other charges in the magazine housing by energizingsolenoid 110 through control line 121 from'a suitable source ofelectrical power (not shown). When a shaped charge is seated atthe'bottom of the well pipe, manifestly the differential pressure acrossthe shaped;charge will An elongated tapered hole will be produced asshown in FIG. 13. I Drilling-fluid circulation will continue so "thatdetritus including earth fragments, fragments of the shaped chargedetonate the charge as described above.

container, and the fragments 53 and 55 of the firing collar 4-5 will becirculated up the annulus, around the well pipe. I 7

One or more gauging charges are landed in succession at the bottom ofthe pipe after each shaped charge. It; will be found that one gaugingcharge is sufficient to enlarge the entire hole to a-desired diameter;As mentioned above, the gauging charges should extend substantially tothe bottom of the hole formed by the jet charge. least a portion of thegauging charge container, will readily seat on the seat 31 so that adifferential pressure will build up to detonate the gauging charge.Manifestly,

the gauging charge will be tamped; a hydrostatic pres sure of at least1000 psi. will be exerted thereon. When a gauging charge is detonated,it will be found that an almost perfect cylindrical hole will be blastedinto the earth formations by the gauging charge. The hole will beamazingly uniform in diameter and will be of a sufficiently largediameter so that the well pipe 28 may be lowered to the depth of thehole blasted by the shaped charge 33. It will be found that, by virtueof the fact that the gauging charge is tarnped and under hydrostaticpressure, the volume of earth that is spalled by the gauging charge willbe between 50 and percent greater than when the explosive charge is nottamped and is not under hydrostatic pressure. A hydrostatic pressure ofat least 1000 pounds has been found to be satisfactory. Much higherhydrostatic pressures may be utilized with the effectiveness of thegauging charge increasing as the hydrostatic pressure is increased.Detritus produced bythe gauging charge may be circulated out of the holeformed as described above, as the well pipe is lowered.

If the Well pipe used as described above is of the type referred to ascasing, cement may be circulated when the borehole has reached desireddepth for the purpose of bonding the pipe to earth formationssurroundingthe borehole. The usual completion techniques may then befollowed and the well produced. In this manner a costly round-trip isavoided.

The invention described above is truly remarkable in that a hole ofuniform diameter comparable to holes drilled by conventional rotarydrill bits may be formed by the sequential use of shaped charges andnondirectionalgaug ing charges. Penetrations of 6 feet and more Collar45a, inasmuch as it is slidable along at may be obtained through earthformations such as limestones, dolomites, quartzites, anhydrite, salt,granite, some shales and some sandstones. Increased drilling rates of upto 400 percent will be obtained in hard formations. Therelative increasein the penetration rate will be found to increase as the formationhardness increases.

The invention is not to be restricted to the specific structuraldetails, arrangement of parts, -or circuit connections herein set forth,as various modifications thereof may be effected without departing fromthe spirit and scope of this invention.

'What is claimed is: V

1. A method of drilling with shaped explosive charges and elongated,nondirectional explosive charges through a well pipe lowerable into aborehole and having explosive charge'landing means at the lower endthereof, comprising: individualy landing said shaped charges at thebottom of the well pipe, and detonating each shaped charge after it islanded so as to blast the earth material below the well pipe; afterdetonation of each shaped charge,-

landing at least one of the elongated, nondirectional charges at'thebottom of the well pipe; extending said at least one nondirectionalcharge from the mouth of the opening left by the immediately precedingshaped charge as far as possible into the hole so that the explosivematerial thereof extends substantially the length of said hole blastedin the earth below the well pipe by the immediately preceding shapedcharge; and detonating each nondirectional explosive charge after it isso landed.

2. A method of drilling with shaped explosive charges and elongated,nondirectional explosive charges through a well pipe lowerable into aborehole and having ex-- plosive charge landing means at the lower endthereof, comprising: circulating drilling fluid down the well pipe andup the annulus therearound; injecting the shaped charges and thenondirectional explosive charges into the stream of drilling fluid goingdown the well pipe according to a predetermined sequence with at leastone nondirectional explosive charge following each shaped charge;detonating the shaped charges as they reach the bottom of the well pipeso that they blast the earth material below the well pipe; insertingeach nondirectional charge into the hole blasted by the immediatelypreceding shaped charge so that said each nondirectional explosivecharge extends from the mouth of the hole as far as possible thereinto;and detonating said each nondirectional explosive charge after it is soinserted.

3. A method of drilling with shaped explosive charges and elongated,nondirectional explosive charges through a well pipe lowerable into aborehole and having explosive charge landing means at the lower endthereof, comprising: circulating drilling fluid down the well pipe andup the annulus therearound; injecting the shaped charges and thenondirectional explosive charges into the stream of drilling fluid goingdown the well pipe according to a predetermined sequence with at leastone nondirectional explosive charge following each shaped charge;detonating the shaped charges asthey reach the bottom of the well pipeso that they-blast the earth material below the well pipe; insertingeach nondirectional charge into the hole blasted by the immediatelypreceding shaped charge until the explosive in said each nondirectionalexplosive charge extends from the mouth of the hole as far as possibleinto said hole; detonating said each nondirectional explosive chargeafter it is so inserted; and circulating Q drilling fluid afterdetonation of each explosive charge for a time interval suflicient toremovedetritus from the bottom of the borehole.

4. A method of drilling with explosive charges through a well pipelowerable into a borehole, comprising: circulating drilling fluid downthe well pipe and up the annulus around the well pipe; injecting shapedcharge capsules into the drilling fluid stream going down the well pipeand seating each capsule at the bottom ofthe well one elongatednondirectional explosive charge into the hole blasted by said eachshaped charge until explosive material extends substantially the lengthof the hole, and detonating said at least one nondirectional explosivecharge; and after detonation of each explosive charge, circulatingdrilling fluid for a period of time sufiicient to clean the detritusfrom the bottom ofthe borehole.

5. A method for drilling with explosive charges through a well pipelowerable into a borehole, comprising: circulating drilling fluid downthe well pipe and up the annulus around the well pipe; injecting shapedcharge capsules into the drilling fluid stream going down the well pipeand seating each capsule at the bottom of the well pipe so that thedirectional explosive eflect of each shaped charge is directeddownwardly; detonating each shaped charge when it is seated at thebottom of the well pipe; after detonation of each shaped charge,inserting atleast one elongated nondirectional explosive charge into thehole blasted by said each shaped charge until explosive material extendssubstantially the length of the hole, and detonating said at least onenondirectional explosive charge while tamping said at least onenondirectional explosive charge with drilling fluid so that thehydrostatic pressure in the: bottom of the borehole is at least 1600pounds per square inch; and after detonation of each explosive charge,circulating drilling fluid for a period.

of time sufficient to clean the detritus from the bottom of theborehole.

6. A method of drilling with explosive charges through a well pipelowerable into "a borehole, comprising: circulating drilling fluid downthe well pipe and up the annulus around the well pipe; injecting shapedcharge capsules into the drilling fluid stream going down the well pipeand seating each capsule at the bottorn of the well pipe so that thedirectional explosive effect of each shaped charge is directeddownwardly; detonating each shapedcharge when it is seated at the bottomof the well pipe; after detonation of each shaped charge, inserting atleast one elongated nondirectional explosive charge into the holeblasted by said each shaped charge until explosive material extendssubstantially the length of the hole, and detonating said at least onenondirectional explosive charge while tamping said at least onenondirectional explosive charge with drilling fluid so that thehydrostatic pressure in the bottom of the borehole is at least 1000pounds per inch; after detonation of each explosive charge, circulatingdrilling fluid for a period of time suffiicient to clean the detritusfrom the bottom of the borehole; and lowering the well pipe afterdetonation of each nondirectional explosive charge.

7. In a method of drilling with shaped charges and nondirectional,elongated explosive charges, wherein the charges are. landed at thelower end of a well pipe and are detonated by differential pressureacross the upper and lower portions thereof, the improvement comprising:circulating drilling fluid down the well pipe and up the annular spacetherearound; injecting the shaped charges and the nondirectionalexplosive charges into the drilling fluid flowing down the well pipeaccording to a predetermined sequence, with at least one nondirectionalexplosive charge following each shaped charge; individually landing theshaped charges in the landing means at the bottom of the well pipe, andincreasing fluid pressure in the well pipe after a shaped charge islanded to detonate the shaped charge and blast the earth material belowthe well pipe; individually landing the nondirectional explosive chargesat the bottom of the well pipe; extending'each nondirectional explosivecharge as far :as possible into the hole left by the immediatelypreceding shaped charge, from the mouth of the hole until explosivematerial extends substantially the length of the hole,

9 and increasing fluid pressure the well pipe after an individualnondirectional explosive charge is landed to detonate the landed charge;and circulating drilling fluid after detonation or each explosive chargefor a time interval snfiicient to remove detritus left in the bottom ofthe borehole.

8. The method set forth in claim 7 wherein each nondirectiona explosivecharge is tamped with drilling fluid so that the hydrostatic pressure atthe bottom of the borehole is at least 1606 p.s.i.

9. In a method of drilling with shaped charges and nondirectional,elongated explosive charges, wherein the charges are detonated bydifierential pressure across the upper and lower portions thereof, theimprovement comprising: circulating drilling fluid down the well pipeand up the annular space therearound; injecting the shaped charges andthe nondirectional explosive charges into the rilling fluid flowing downthe well pipe according to a predetermined sequence, with at least onenondirectional explosive charge following each shaped charge;individually landin the shaped charges at the bottom of the well pipe,and increasing fiuid pressure in the well pipe after a shaped charge islanded to detonate the shaped charge and blast the earth material belowthe well pipe;

individually landing the nondirectional explosive charges at the bottomof the well pipe; extending each nondirectional explosive charge as faras possible into the hole left by the immediately preceding shapedcharge from the mouth of the hole until explosive material extendssubstantially the length of the hole, and increasing fluid pressure inthe well pipe after an individual nondirectional explosive charge islanded to detonate the landed charge; circulating drilling fluid afterdetonation of each explosive charge for a time interval sufiicient toremove detritus left in the bottom of the borehole; and lowering thewell pipe in the borehole after detonation of each nondirectionalexplosive charge.

References Cited in the file of this patent UNITED STATES PATENTS1,585,664 Gilinan May 25, 1926 2,679,380 Sweetman May 25, 1954 2,749,840Babcock June 12, 1956 2,869,825 Crawford Jan. 20, 1959 2,897,756 Borinset al. Aug. 4, 1959 FOREIGN PATENTS 1,0 22,350 France Dec 17, 1952

